Field
Embodiments of the disclosure relate generally to thermal energy harvesting for electrical power and more particularly to a system employing alternating flow control of hot and cold air streams through a shape memory alloy (SMA) tube providing rotation to an output shaft connected to a generator.
Background
There is a growing need for electrical power on modern aircraft. Everything from flight control surfaces to entertainment systems require more and more electrical power. At the same time, in the face of increasing demands for reduced emissions, engines are becoming more and more efficient and therefore have much less excess power available to be used for generating electrical power. Additionally the large number of electrical systems on modern aircraft also requires a significant amount of heavy and complex wiring. Existing methods for supplying energy to electrically powered systems, such as the environmental control system (ECS), rely exclusively on power generated by the engines or auxiliary power unit (APU). Ground power may be used for ground operations, however in flight electrical power is provided by the increasingly taxed engines.
Shape memory actuator (SMA) systems have been employed in the prior art for energy harvesting by converting thermal energy to motion which is then employed for electrical energy generation. Typical prior art systems usually rely on two separated and stationary hot and cold zones and use a complex kinematic device that is powered by the shape change of the SMA component. As an SMA element heats up it literally moves itself out of the hot zone and into the cool zone, as it cools the subsequent shape change moves it back to the hot zone where the process is repeated. These methods often produce large motions, but very little work and only small amounts of electrical power are generated.
It is therefore desirable to provide an efficient system for energy harvesting which can provide local power to reduce wiring runs and supplement engine and APU power.